Energy Loss of Cosmic Rays in the Interplanetary Medium

Abstract
The expansion of the solar wind is likely to cause low-energy cosmic-ray particles to lose a significant fraction of their energy in the interplanetary medium. It is shown that because of this effect, most of the protons observed below ∼100 MeV and alpha particles below ∼60 MeV/nucleon originate at higher energies, making it impossible to sample directly the interstellar spectra at these energies.